The present invention relates to a circuit for the real time analysis of the energy distribution of the pulses of a pulse signal. In this circuit, the energy distribution of the pulses is defined by the counting of the number of pulses in predetermined energy windows or energy bands. This circuit makes it possible to analyze the energy distribution of non-stationary physical phenomena, such as the radioactive disintegration or decay of a radioactive substance.
It is known that the mass of a radioactive substance contained in a material constituted by several elements can be determined by the disintegration or decay rate of said substance. The particle or electromagnetic radiation associated with this decay has a perfectly defined energy. As each decay is converted into a pulse, the counting of the pulses falling in an energy window centred on said decay energy makes it possible to evaluate the decay rate of said substance. It should be noted that if the material has several radioactive substances, the mass of each of them can be determined if the energy windows associated with these radioactive substances are separate.
The counting rate in each energy window results from superimposing the decays of the radioactive substance and the background noise due to cosmic radiation and to the terrain where the measurement is performed. This background noise is evaluated by counting the pulses falling into an energy window which is independent of the other energy windows and in which no decay is possible due to an analyzed radioactive substance. The real decay rate of each analyzed radioactive substance is consequently determined by the counting rate in the associated energy window, less the counting rate due to the background noise.
The known circuits for analyzing the energy distribution of the pulses of a pulse signal comprise an analog-digital converter supplying a digital code representing the amplitude of the pulse received, a storage means having the same number of storage cells as there are possible values of the digital code and processing means for incrementing the content of the storage cell associated with the digital code supplied by the analog-digital converter.
When the count is finished, the informations contained in each storage cell represent the energy distribution of the measured phenomenon. This energy distribution is defined by the number of pulses per channel or energy level.
If it is wished to know the energy distribution of the pulses of the signal measured by energy windows, it is necessary to add the numbers contained in all the channels corresponding to the same energy window. This treatment can only take place after the end of the analysis of the measured signal leading to a not insignificant paralysis time between two consecutive analyses.